Saimiri oerstedii occurs along the Pacific coast of Costa Rica and Panama inland to altitudes of up to 500 m asl. The north-eastern limit is marked by the Río Tulín in the north Herradura Mountains (9°40’N, 84°35’W) and Dota Mountains (9°37’N, 84°35’W). Along the coast of the Golfo Dulce and the Burica Peninsula to the western part of the Chiriquí Province, mouth of the Río Fonseca, including the Archipelago of the Golfo de Chiriquí, in Panama (Hershkovitz 1984; Boinski et al. 1998; Reid 1997).

There are two subspecies:

Saimiri oerstedii oerstedii occurs along the Pacific coast of Costa Rica, from the left bank of the Río Grande de Térraba to the Osa Pensinsula, along the coast of the Golfo Dulce and the Burica Peninsula to the western part of the Chiriquí Province, mouth of the Río Fonseca, including the Archipelago of the Golfo de Chiriquí, in Panama (Hershkovitz 1984; Boinski et al. 1998; Reid 1997). Surveys by Baldwin and Baldwin (1972, 1976) recorded its presence on the Burica Peninsula, but indicated that it is now restricted to a narrow strip of scattered lowland coastal forest fragments, not extending to the type locality David, although it possibly occurred as far east as Remedios (well to the east of David) prior to the 1950s. Altitudinal range is 0 to 500 m asl (Hershkovitz 1984). Rodríguez-Vargas (2003) mapped the remaining populations in Panama.

The historic range of Saimiri oerstedii citrinellus is along the Pacific coast of Costa Rica, to altitudes of up to 500 m asl. The north-eastern limit is marked by the Río Tulín in the north Herradura Mountains (9°40’N, 84°35’W) and Dota Mountains (9°37’N, 84°35’W), and the southern limit is the north bank of the Río Grande de Térraba (8°25´N, 84°25´W) (Arauz 1993; Sierra et al. 2003). Its occurrence is sporadic, and the surviving populations are entirely fragmented (Alfaro 1987; Wong 1990; Sierra et al. 2003).

Typically prefers seasonally inundated forests, river edge forest, floodplain, and secondary forests (see Boinski 1987c). They use all levels of the forest, but forage and travel mainly in the lower canopy and understorey. Locomotion involves predominantly quadupredal walking and running

Squirrel monkeys are small frugivore-insectivores. They spend 75-80% of their day foraging for insects and other small animal prey (Mittermeier and Van Roosmalen 1981; Terborgh 1983; Boinski 1988). During dry season shortages of appropriate fruiting trees they are able to depend entirely on animal prey (Janson and Boinski 1992).

Saimiri groups are multi-male and can be large, up to 100 animals (larger groups are believed to be temporary mergers of two) but most frequently are of 20-75 individuals (Baldwin and Baldwin 1981; Terborgh 1983; Mitchell et al. 1991). As emphasized by Boinski (1999a,b; 2005; Boinski et al. 2005a,b) allthough all squirrel monkeys are morphologicallly very similar, their social systems are quite distinct (summarized in Sussman 2000).

In S. oerstedii, females do not form dominance hierarchies, and there is no evidence of coalition formation in social interactions. Females transfer between groups before first mating season, and males are philopatric. There is little competition or agonistic interactions between groups, and males show high levels of vigilance for predators. Reproductively mature males collaborate in mobbing females during the mating season. Their fruits they typically exploit occur in small and very scarce patches, and feeding competition is very low.

Mating and births in Saimiri are highly seasonal, seldom exceeding two months in duration (see Boinski 1987a,b). Single offspring, qwith interbirth intervals of about 12 months (Boinski 1999b). Mating usually occurs during the dry season. In S. oerstedii, sexual receptivity in females is synchronized, and lasts only one or two days each season. In S. sciureus, birth synchrony is less pronounced and births occur only once every two years.

Costa RicaManuel Antonio National Park (683 ha) (Boinski and Sirot 1996; Matamoros et al. 1996; Matomoros and Seal 2001)Carara Biological Reserve (4,700 ha) (Rodríguez-Luna et al. 1996a,b; just to north of known range, not confirmed) - this subspecies has not been seen in this protected area Cerro de Turrubares Protection Zone (2,340 ha) (Rodrigues-Luna et al. 1996; within historic range, not confirmed).

In-Place Research, Monitoring and PlanningIn-Place Land/Water Protection and Management Conservation sites identified:Yes, over entire rangeIn-Place Species ManagementIn-Place Education Subject to recent education and awareness programmes:Yes Included in international legislation:Yes Subject to any international management/trade controls:Yes

Hershkovitz, P. 1987. Uacaries, New World monkeys of the genus Cacajao (Cebidae, Platyrrhini): a preliminary taxonomic review with the description of a new subspecies. American Journal of primatology 12: 1–53.